Config: fix filter argument case in help texts (#3879)

The filter names are case-sensitive (depending on OS), so the help texts should display the case which will be accepted on all OS-es.

src/Config.php

@@ -1403,7 +1403,7 @@ public function printPHPCSUsage()
         echo '                e.g., module/php,es/js'.PHP_EOL;
         echo ' <file>         One or more files and/or directories to check'.PHP_EOL;
         echo ' <fileList>     A file containing a list of files and/or directories to check (one per line)'.PHP_EOL;
-        echo ' <filter>       Use either the "gitmodified" or "gitstaged" filter,'.PHP_EOL;
+        echo ' <filter>       Use either the "GitModified" or "GitStaged" filter,'.PHP_EOL;
         echo '                or specify the path to a custom filter class'.PHP_EOL;
         echo ' <generator>    Use either the "HTML", "Markdown" or "Text" generator'.PHP_EOL;
         echo '                (forces documentation generation instead of checking)'.PHP_EOL;
@@ -1465,7 +1465,7 @@ public function printPHPCBFUsage()
         echo '               e.g., module/php,es/js'.PHP_EOL;
         echo ' <file>        One or more files and/or directories to fix'.PHP_EOL;
         echo ' <fileList>    A file containing a list of files and/or directories to fix (one per line)'.PHP_EOL;
-        echo ' <filter>      Use either the "gitmodified" or "gitstaged" filter,'.PHP_EOL;
+        echo ' <filter>      Use either the "GitModified" or "GitStaged" filter,'.PHP_EOL;
         echo '               or specify the path to a custom filter class'.PHP_EOL;
         echo ' <patterns>    A comma separated list of patterns to ignore files and directories'.PHP_EOL;
         echo ' <processes>   How many files should be fixed simultaneously (default is 1)'.PHP_EOL;